Bleeding in the brain is usually a dangerous event, particularly if blood is lost from a major blood vessel.

Although haemorrhagic stroke is one of the major causes of spontaneous bleeding in the brain, there are others, including brain aneurysm, subarachnoid haemorrhage, and rare genetic and blood disorders.

The brain is a delicate tissue that needs a constant supply of fresh blood to be able to get enough oxygen and fuel to work well. Bleeding in the brain can damage brain tissue directly and it can also lead to increased intracranial pressure. This can cause widespread damage.

When bleeding in the brain occurs after an accident or injury, it is caused by trauma. This is an external event that can cause the bleed to happen even in healthy tissue. When blood vessels spill blood into the brain because of an underlying disease process, we call this type of bleeding in the brain a spontaneous bleed.

Bleeding in the brain due to haemorrhagic stroke

Most acute strokes (about 70%) are due to a blockage in one of the arteries that bring oxygenated blood into the brain. These are usually caused by atherosclerosis, which narrows the arteries and leads to an ischaemic stroke.

Around 15 in every 100 people who have a stroke do so because one of the blood vessels in their brain bursts, releasing blood into the brain tissue. This event is a haemorrhagic stroke and it can also be called an intracerebral haemorrhage; the spill of blood that it causes is an intracerebral hematoma.

The symptoms of a haemorrhagic stroke are similar to those of an ischaemic stroke but the treatment needed is quite different. Clot busting drugs and anticoagulants are used to help unblock a blood vessel if someone has had an ischaemic stroke but this would be highly dangerous in someone who has bleeding in the brain.

This is why it is important for anyone admitted to hospital with a stroke to undergo a CT scan or MRI scan very quickly. These imaging techniques can show which type of stroke has taken place. For someone who has had a haemorrhagic stroke, the best treatment is usually emergency surgery to stop the bleeding in the brain and to get rid of the blood that has spilled into the brain tissue.

High blood pressure and bleeding in the brain

The most common reason for a haemorrhagic stroke is high blood pressure. This produces no obvious symptoms, so someone can have raised blood pressure for a long time without knowing it. Although the person affected may feel fine, the extra force of blood passing through the blood vessels in their brain is causing problems. Arteries can weaken under this pressure, and eventually break down, causing bleeding in the brain.

Reducing blood pressure by taking on a healthier lifestyle, and by taking drugs to lower blood pressure as necessary, can reduce the risk of a haemorrhagic stroke.

Bleeding in the brain caused by a subarachnoid haemorrhage

Spontaneous bleeding in the brain can also arise in the subarachnoid space, which is in-between the membranes that surround the brain. This form of bleed is called a subarachnoid haemorrhage and accounts for about one in 20 strokes. The most usual cause is found to be an aneurysm near to the surface of the brain that has burst.

Bleeding in the brain due to a brain aneurysm

A brain aneurysm is another blood vessel problem that is caused by atherosclerosis. Fats and debris build up on the inner surface of the arteries, causing them to become less elastic and the walls weaken. This often happens in older people and tends to affect blood vessels throughout the body. People who have atherosclerosis also have high blood pressure, and this causes the artery to balloon out at the point where it is weakest.

A brain aneurysm doesn’t always burst; it can grow to a certain size and then remain there, or it can grow. Small and large aneurysms can burst and the degree of damage to the brain depends on the quantity of blood released, which part of the brain is affected, and how quickly treatment can be given. People can show symptoms if they have a brain aneurysm that hasn’t burst and imaging techniques can then be used to monitor the aneurysm regularly.

The usual treatment is then planned surgery or a technique called endovascular coiling, where a coil is placed into the aneurysm through one of the main veins. A burst aneurysm leads to the same effects as a haemorrhagic stroke and usually needs emergency treatment.

Less common causes of bleeding in the brain

Although stroke and high blood pressure, brain aneurysms and subarachnoid haemorrhage are the major causes of bleeding in the brain, specific conditions can also increase risk:

  • Blood vessel abnormalities such as arteriovenous malformations (AVMs) can cause bleeding in the brain. The amount of blood lost is usually small, and may cause few problems. Treatment may become urgent in some cases, but not in all. Most cases are thought to be congenital where the problem develops during development in the womb but symptoms only start to appear much later in life. Many AVMs are only diagnosed after they cause significant bleeding in the brain, which produces the same symptoms of a haemorrhagic stroke.
  • Cavernomas are also due to blood vessel malformations but they rarely cause large bleeds in the brain. They can be unstable and release small amounts of blood, which can lead to symptoms.
  • Amyloid angiopathy is a condition that is caused by the build up of amyloid deposits in the blood vessels in the brain. It occurs in older people and is linked with Alzheimer’s disease. Amyloid deposits can occur in both the brain tissue and the blood vessels.
  • Blood disorders such as sickle cell anaemia and haemophilia both lead to abnormal and unpredictable bleeding in the brain and other parts of the body. Fortunately, both can now be controlled with drug therapy and careful monitoring.
  • Anti-coagulant drug therapy can increase the risk of bleeding generally, but does increase the chances of a haemorrhagic stroke if bleeding in the brain occurs.
  • Rare genetic disorders such as neurofibromatosis, Marfan syndrome and Ehlers-Danlos syndrome can increase the risk of blood vessel weakness, leading to a higher risk of stroke and aneurysm.